Piston internal combustion engine with reinforced engine block using segmented ribs

ABSTRACT

A piston internal combustion engine includes an engine block made of a base material and including a cylinder block having walls. Segmented, rib shaped reinforcements are disposed on the engine block, each reinforcement defining breaks along a course thereof, the reinforcements further being made of a material having a higher modulus of elasticity than the base material.

BACKGROUND OF THE INVENTION

In operation, piston engines, in particular piston internal combustionengines, are excited to vibrate as a function of the changing events inthe cylinder chamber, such as the course of combustion, but also as afunction of mechanical influences. The vibrations are also radiated asnoise at the surfaces of the piston engine in the form of airbornenoise, and/or are transmitted via the bearings of the piston engine intothe substructure or into the body in vehicles as structure-borne sound.

Abatement of noise emissions of the above kind is sought, because oftheir negative effects on humans and the environment. DE-A-28 49 613attempts to produce a noise shield by disposing an elastic acousticalinsulation enclosure, which is attached to the engine block of a pistoninternal combustion engine. Furthermore, DE-A-28 01 431 suggestssupporting the entire piston internal combustion engine in an outertublike casing with the aid of support elements, which insulatestructure-borne sound. A disadvantage of such an acoustical insulationmeasure is that it contains a large part of the machine and thereforehinders the installation of add-on parts and/or additional units, suchas engine mounts, starter, generator, or gas supply lines and gasexhaust lines. In this connection, in many cases, it is impossible toprevent the breaching of acoustical insulation enclosures of the abovekind in order to install add-on parts of the same kind and/or additionalunits, which measure reduces the effectiveness of the arrangement.Furthermore, acoustical insulation measures of the above kind reduce theheat tolerance of a piston internal combustion engine.

On account of the above mentioned disadvantages, there have beenattempts to control noise propagation by seeking to prevent or at leastto reduce the generation of noise. In addition to reducing sources ofexcitation, for example by optimizing the combustion process, it makessense primarily to reduce the noise transmission and noise radiation atthe surfaces of the piston engine. The above is achieved by configuringthe piston engine to be as rigidly as possible, particularly making itresistant to bending, or torsionally rigid, especially in itsthin-walled regions; the oscillatory faces are configured to be as smalland/or thick-walled as possible with regard to airborne noise radiation.According to the above arrangement, however not only is there then anundesired increase in weight, particularly resulting from an increase inwall thickness, primarily in cast components, but increased castingdefects such as bubbles or pores or the like also occur. DE-A-35 44 215has already suggested improving the rigidity of the engine block as awhole with a system of reinforcement ribs on the side walls in thecylinder region. As a result, undesired casting defects can be preventedby configuring the ribs in this way, and high rigidity of the cylinderblock can be achieved.

DE-A-40 17 139 suggests the concept of achieving the required rigidityof the engine block via the purposeful installation of bands and ribs.According to this proposal, the above is achieved in particular bybinding the crankshaft bearings to the cylinder block and to the sidewalls of the crankcase via a multitude of reinforcing ribs, so that therigidity of the engine block structure as a whole is increased. However,the above arrangement entails a corresponding increase in weight.However, from an economical standpoint, a weight increase is to beavoided.

SUMMARY OF THE INVENTION

The object of the invention, is to reduce the vibration and noisegeneration of a piston engine, in particular of a piston internalcombustion engine, by the design of the engine block structure withoutincreasing the overall weight if at all possible.

The above object is attained according to the invention with a pistonengine, in particular a piston internal combustion engine, in whichcylinders, pistons, the crankshaft, and crankshaft bearings are disposedin an engine block, and regions on the engine block are provided withcap- and/or cup-shaped coverings, and in which the walls of the engineblock and/or the coverings, are provided, at least in some regions, withrib-shaped reinforcements which run in a segmented line. The particularadvantage of the invention is that the free oscillatory outer faces ofthe engine block structure are reduced, and the acoustic behavior of theengine block structure is audibly improved. Ribs of the above kind leadto an increased impedance discontinuity at the break points betweensegments, and consequently lead in particular to a reduction in thetransmission of structure-borne sound. The geometry of the break pointscan for example be as wedge-shaped, trapezoidal, or rounded.

In terms of the present invention, the coverings include, for example,the cylinder head cover, control drive coverings, the crankcase oroilpan, and similar elements of the engine structure. With a view toreducing noise, which is the object of the present invention, inparticular in piston internal combustion engines, the transmissionsconnected to the engine also have to be taken into account, since eventhe walls of a flange mounted transmission case, for example, canradiate noise. Here, too, a vibration reducing reinforcement can beachieved with an arrangement of components in the wall. In the samemanner, the intake and/or exhaust pipes can be reinforced in a vibrationreducing manner on the inside with tubular components and/or on theoutside with strut- or rib-shaped components, so that via thesestructures, which in the broad sense belong to the engine block, nonoise radiation or only slight noise radiation is produced.

The rib-shaped reinforcements can be comprised of the base material ofthe engine block, for example cast with cast engine blocks or engineblock parts.

In one embodiment of the invention, for the rib-shaped reinforcements,materials which have a higher modulus of elasticity than the basematerial of the engine block can be provided, these being particularlyceramic materials. These materials have a much higher modulus ofelasticity than the standard gray cast iron or cast aluminum used forthe base material. In the event that gray cast iron is used as the basematerial, the density of ceramic materials is essentially lower than thedensity of the base material. With the use of cast aluminum, the densityof the ceramic materials is approximately the same. Because of thesematerial properties, reinforcing components of ceramic materials, withthe same mass, can produce approximately twelve times the rigiditycompared to a structurally similar embodiment of gray cast iron. For thesame rigidity, for example, ribs of a ceramic material haveapproximately 70% less mass than ribs of gray cast iron. A furtheradvantage is that with a rib-shaped embodiment of such components, witha predetermined equal rigidity given the higher modulus of elasticity,the geometric dimensions are reduced compared to a rib of the basematerial, so that the structural volume of the engine is reduced.Reinforcing measures for noise reduction can therefore be effectivelyintroduced into the components, even with an existing production system.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be explained in further detail in terms of anexemplary embodiment, in conjunction with a schematic drawing of anengine block according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the drawing, an engine block 1 of a four-cylinder piston internalcombustion engine is shown, whose upper section constitutes the cylinderblock 2 and whose lower section constitutes the upper part of thecrankcase 3. The crankcase 3 is enclosed on the underside with a tublikecrankcase bottom, not shown. The cylinder block 2 and the crankcase 3are embodied as one component, particularly in vehicle engines. Toreinforce the structure, rib-shaped reinforcements, which extend in thelongitudinal direction of the engine, are disposed on the cylinder block2 and likewise on the crankcase 3. These rib-shaped reinforcements 4 canbe comprised of the base material of the engine block 1 and can bejoined by material adhesion, for example by the casting process. Theycan also be comprised of a material, which has a higher modulus ofelasticity than the base material, preferably of a ceramic material. Ifthe engine block 1 is made for example of gray cast iron, then comparedto the gray cast iron base material, the reinforcements 4 have forexample a modulus of elasticity approximately three times higher thanand about half the density of the base material. The thermal expansioncoefficient is similar to that of gray cast iron, so that a composite ofgray cast iron and ceramic is not problematic from this standpoint. Ifaluminum is used as the base material, the reinforcements 4, for examplewith the use of aluminum oxide ceramic, have a modulus of elasticityfive times higher than the base body at a similar density. Thus whengray cast iron is used for the base body, for example, the above kind ofceramic rib-shaped reinforcement 4, as shown in the drawing, has around70% less mass than ribs of gray cast iron, with the same inherentstability. Rib-shaped reinforcements of the above kind can be disposedon the crankcase 3, both on the outer wall and on the inner wall. In theapparatus shown, the rigidity of the engine block increases globally andabove all, locally in particular with regard to the vertical engine axisso that the production of vibrations is hindered and the amplitude ofthe produced vibrations of the engine block is decreased.

As can be seen in the drawing, the rib-shaped reinforcements 4, whichextend in the longitudinal direction, are interrupted or segmented intheir longitudinal direction; the breaks 5 are provided preferably inthe region of the connecting points of the bearing walls with the outerwalls of the engine block, that is, in locations at which structurallyrequired wall thickenings are provided anyway. Thus, the freeoscillatory outer faces of the engine block structure are reduced insize, and the acoustic behavior of the engine block structure is audiblyimproved. Rib courses which are segmented in this way lead to anincreased impedance discontinuity at the break points 5 and consequentlyto a reduction of structure-borne sound transmission. The geometry ofthe break points can be wedge-shaped or trapezoidal, as shown forexample for the region 5.1, or can be rounded, as shown for the region5.2.

The rib-shaped reinforcements can be provided in larger wall faces onthe engine block or also on its various cap- and/or cup-shapedcoverings, even in a crosswise disposition. It is important only thatthey are each segmented in their longitudinal span.

If the rib-shaped reinforcements are comprised of a material other thanthe base material, these can be connected to the relevant regions of theengine block by recasting, gluing, soldering, or welding.

We claim:
 1. A piston internal combustion engine, in which cylinders,pistons, crankshaft, and crankshaft bearings are disposed in an engineblock made of a base material, wherein regions on the engine block areprovided with at least one of cap-shaped and cup-shaped coverings inwhich at least one of walls of the cylinder block and the coverings, atleast in some regions, are provided with segmented, rib-shapedreinforcements defining breaks therein, and wherein a ceramic materialfor the rib-shaped reinforcements with a higher modulus of elasticitythan the base material of the engine block is used.
 2. The piston engineaccording to claim 1, characterized in that the breaks in the rib-shapedreinforcements are each provided in regions of structurally requiredwall thickenings.
 3. A piston internal combustion engine comprising:anengine block made of a base material and including a cylinder blockhaving walls; and segmented, rib shaped reinforcements disposed on theengine block, each reinforcement defining breaks along a course thereof,the reinforcements further being made of a material having a highermodulus of elasticity than the base material.
 4. The piston internalcombustion engine according to claim 3, further comprising coveringscoupled to predetermined regions of the engine block, wherein thereinforcements are disposed on at least one of the coverings and thewalls of the cylinder block.
 5. The piston internal combustion engineaccording to claim 4, wherein the coverings are at least one ofcap-shaped and cup-shaped.
 6. The piston internal combustion engineaccording to claim 3, wherein:the engine block includes thickened wallsat predetermined portions thereof; and the reinforcements are disposedon the engine block such their breaks are located at the predeterminedportions of the engine block which include the thickened walls.
 7. Thepiston internal combustion engine according to claim 3, wherein thematerial having a higher modulus of elasticity than the base materialcomprises a ceramic material.
 8. The piston internal combustion engineaccording to claim 6, wherein the material having a higher modulus ofelasticity than the base material comprises a ceramic material.